GREENSBORO, N.C.-- Monday, Guilford County Schools announced that Northern High School violated a Carolina High School Athletic Association (NCHSAA) rule, but the school reported it immediately.

The violation happened Friday, September 13 in the game against Williams High School. According to NCHSAA rules, up to 12 junior varsity players are allowed to play in a varsity game. However, 13 junior varsity players participated for Northern High in that game.

School officials discovered the mistake the day after the game and immediately reported it to district staff, according to a news release from GCS.

More from the GCS release:

District officials reported the violation to the NCHSAA, which determined this was an eligibility violation. Northern will forfeit the win against Williams, essentially ending a 31-game winning streak.

"Our students, staff and community are disappointed that this happened, and that we have to forfeit last week's game," said Northern Principal Will Laine. "But the most important thing we can teach our students is to follow the rules. When you make a mistake, you own up to it and work to make sure it doesn't happen again."

GCS follows NCHSAA rules for interscholastic athletic contests. Those rules require districts to report players who are determined ineligible. Consequences for violations are determined by the NCHSAA, and can include forfeiting games, as well as a fine. Since GCS self-reported the violation, the resulting $500 fine was cut in half to $250.